The present invention relates to fluid metering and spraying and, more particularly, to orifices for the passage of fluid which may contain solid particulate contaminants and nozzles and methods for metering and dispensing such fluids all of which preclude plugging by the contaminants.
In U.S. Pat. No. 3,672,578 of Alex Wayne, a fluid nozzle is disclosed in which fluid is caused to flow through an elongated passage from which it is injected into a chamber prior to discharge from the discharge orifice of the nozzle. The elongate passage is angularly disposed to cause the fluid to enter the predischarge chamber in a swirling fashion. The elongate passage not only imparts a swirling motion to the fluid in this chamber and upon discharge from the nozzle, but also constitutes an orifice which meters the quantity of fluid discharged from the nozzle and, thereby, determines the capacity of the nozzle.
Nozzles such as disclosed in the aforementioned patent have found wide application as fuel oil burner nozzles for the injection of the fuel oil in metered quantities into oil furnaces. These nozzles operate quite satisfactorily where the flow rate through the nozzles is substantial, particularly where the fuel oil which is being passed through the nozzle has been filtered to remove solid particulate contaminants to the extent that this is possible. However, an increasing demand exists today for fuel oil burner nozzles of substantially lower flow rates or capacities than have been generally used in the past due to the increased usage of fuel conserving structural techniques and increased fuel prices. Moreover, there is a continuing need for such low flow rate nozzles for the heating of small volume residences, such as mobile homes and the like.
Nozzles such as disclosed in the aforementioned patent have been found to be unsatisfactory in such low flow rate applications, for example where the flow rate does not exceed 0.4-0.5 gallon per hour at 100 psi of No. 2 fuel oil. The reason is that even though filters, such as sintered filters, are available for removing the major portion of the solid contaminants in the fuel oil entering the nozzles, such filters still can not remove all of the extremely fine solid particulate contaminants in the micron size ranges. These fine contaminants do not present a problem in the higher flow rate nozzles where the metering passages or orifices are larger because these fine contaminants easily pass through these orifices. However, where the size of the metering passages or orifices are necessarily reduced to obtain the lower fuel oil flow rates and capacities, these fine contaminants which pass through the filter become lodged in the metering passages or orifices and quickly cause them to plug so as to render the nozzle inoperative.
It has been discovered in the present invention that the metering orifices or passages in such low flow rate nozzles may be reduced in size to achieve flow rates at or below the 0.4-0.5 gallon per hour rates if they are configured in a certain manner as herein described and, if they are so configured, they avoid plugging by fine contaminants. Indeed, it has been found that by practicing the principles of the present invention, flow rates of as low as 0.25 gallon per hour at 100 psi with No. 2 fuel oil may be readily obtained without plugging and inoperability of the fuel oil nozzles. Another advantage of the present invention is that these low flow rates may be obtained at a minimum of manufacturing and maintenance expense.
In one principal aspect of the present invention, an orifice for the passage of fluid which may contain solid particulates includes an opening which is substantially rectangular in a cross-section plane perpendicular to the axis of the fluid flow therethrough. The opening has a ratio of minimum width to minimum depth, or vice versa, of less than approximately 1.5, and preferably approximately 1.0, and a ratio of the length of the opening to the lesser of minimum width and minimum depth of the opening of less than approximately 2.0, and preferably approximately 1.0.
In another principal aspect of the present invention, a fluid nozzle having a discharge orifice, a chamber for swirling fluid upstream of the discharge orifice, and second orifice means for introducing the fluid into the chamber and for imparting swirl to the fluid includes the improvement in which the second orifice means includes at least one opening which is smaller in cross section than the discharge orifice and which is substantially rectangular in a cross-sectional plane perpendicular to the axis of the fluid flow through the opening. The opening has a ratio of minimum width to minimum depth, or vice versa, of less than approximately 1.5, and preferably approximately 1.0.
In still another aspect of the present invention, a method of metering fluid which may contain solid particulates includes passing the fluid through an orifice having at least one opening which is substantially rectangular in a cross-sectional plane perpendicular to the axis of the fluid flow through the opening. The opening has a ratio of minimum width to minimum depth, or vice versa, of less than approximately 1.5 and preferably approximately 1.0, and a ratio of length to the lesser of minimum width and minimum depth of less than approximately 2.0, and preferably approximately 1.0.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.